The major themes of this program are the development and improvement of methods for determination of myocardial blood flow in patients using emission tomography, and the development of new techniques for myocardial NMR spectroscopy. Four projects and 2 cores comprise this program which has essential collaborations with Univ. of California at San Francisco, Palo Alto Veteran Administration Hospital, Boston University, Duke University and the University of Pennsylvania. Project 1 includes development and clinical evaluation of quantitative cardiac PET using generator produced radiopharmaceuticals, 82Rb and 68Ga- complexes, and development of dynamic SPECT for nuclear cardiology. Project 2 is a technology development activity aimed to develop a new detector module to overcome count-rate limitations of contemporary PET instruments. Project 3 will establish the safe thresholds for the amplitude of rapidly oscillating magnetic fields proposed for new NMR techniques in Project 4 as well as techniques being proposed for cardiac studies throughout the world. This project will also study the electrophysiology of cardiac muscle excitation. Project 4 advances new techniques for spectroscopic imaging with oscillating magnetic field gradients for non-invasive studies of biologically important NMR nuclei in the heart. The core support programs involve deployment of mathematical algorithms for reconstructive tomography and kinetic analysis, biostatistics, data analyses and program administration. Major contributions expected from this program are the proof of whether wash-in rate parameters will give significantly more sensitive information for the detection of perfusion defects than examination of static accumulation images with and without stress; development of the capabilities of dynamic cardiac SPECT, development of the essential component to enable production of high count-rate commercial cardiac PET instruments; establishment of the thresholds for cardiac excitation for oscillating magnetic fields of various frequencies; and development of new NMR spectroscopic imaging techniques for studying Na, K, and metabolic compounds in the beating human heart.